A superconducting fault current limiter (SCFCL) is a device that limits fault currents in a power system. The power system may include transmission and distribution networks to deliver power to differing industrial, commercial, and residential loads. A fault current is an abnormal current in the power system due to a fault such as a short circuit. A fault current may occur due to any number of events such as severe weather damaging power lines and components, e.g., lighting striking the power system. When faults occur, a large load appears instantaneously. The network, in response, delivers a large amount of current fault current) to this load or, in this case, the fault. This surge or fault current condition is undesirable since it may damage the network or equipment connected to the network.
A SCFCL includes a superconductor positioned in a cryogenic tank. The superconductor is in a superconducting state having zero resistance during normal or steady state operation. To maintain the superconductor in the superconducting state, the superconductor is operated below its critical temperature, critical current density, and critical magnetic field. If any one of these three is exceeded, the superconductor quenches from its superconducting state to a normal state and exhibits a resistance. To maintain the superconductor at a temperature below its critical temperature, a refrigeration system provides a cryogenic cooling fluid to the cryogenic tank housing the superconductor. The conventional refrigeration system strives to maintain a constant temperature of the cooling fluid sufficiently below the critical temperature of the superconductor. One drawback with this is the energy needed to maintain the selected constant temperature. Another drawback is that the fault current necessary to quench the superconductor may be excessive leading to a comparatively slower transition to quenching when a fault occurs. Therefore, the protective advantage of the SCFCL may be diminished as the peak-to-peak amplitude of the current passed during a fault condition may be higher than desired.
Accordingly, there is a need in the art for an SCFCL that overcomes the above-described inadequacies and shortcomings.